1. Field of the Invention
The present invention relates to an actinic-ray- or radiation-sensitive resin composition that can find appropriate application in an ultramicrolithography process for the manufacturing of a super-LSI, a high-capacity microchip, etc. and other photofabrication processes, from which a high-definition pattern can be formed with the use of electron beams or extreme ultraviolet, and relates to a method of forming a pattern in which the composition is used. More particularly, the present invention relates to an actinic-ray- or radiation-sensitive resin composition that can find appropriate application in a process in which use is made of a substrate with a specified foundation film and relates to an actinic-ray- or radiation-sensitive film therefrom, a mask blank and a method of forming a pattern.
2. Description of the Related Art
In the microfabrication using a resist composition, the formation of a nanopattern is required in accordance with the realization of high integration for integrated circuits. In accordance with this requirement, the trend of exposure wavelength toward a short wavelength, for example, from g-rays to i-rays and further to an excimer laser light is seen. Now, for example, the development of lithography technology using electron beams is progressing. With respect to the resins exposed to an excimer laser light, such as a KrF excimer laser light, patent references 1 to 4 disclose a resin with a structure resulting from replacement of the hydrogen atom of a phenolic hydroxyl group with a group containing an aliphatic hydrocarbon residue, a resin with a structure resulting from replacement of the hydrogen atom with a group containing an aryl group, a resin with a structure resulting from replacement of the hydrogen atom with an alkyl group and a resin with a structure resulting from replacement of the hydrogen atom with a linear alkyl group in which an oxirane group is introduced, respectively. For the formation of a nanopattern, the thickness of the resist film must be reduced. However, the reduction of the film thickness leads to a poor dry etching resistance.
In the electron beam lithography, in recent years, the influence of electron scattering (forward scattering) in a resist film is lessened by increasing the acceleration voltage of electron beams (EB). However, this lowers the electron energy trapping ratio in the resist film, thereby rendering the sensitivity poor, and increases the influence of the scattering of electrons reflected by the resist substrate (backward scattering). In particular, when it is intended to form an isolated pattern of large exposure area, the influence of backward scattering is grave, thereby deteriorating the resolution of the isolated pattern.
In particular, in the patterning of a photomask blank for use in semiconductor exposure, as a light shielding film containing a heavy atom is present in a resist underlayer, the influence of backward scattering attributed thereto is highly conspicuous. Therefore, when an isolated pattern is formed on a photomask blank, the possibility of resolution deterioration is especially high.
The use of a resin with an aromatic skeleton such as naphthalene (for example, patent references 5 and 6) and the use of a resin containing an oxirane group (for example, patent reference 7) are being studied as means for solving these problems. However, the resolution of an isolated pattern remains unsolved. Further, in the technology disclosed in patent reference 7, an unsatisfactory dry etching resistance has been proved. In patent reference 8, a resin containing a group capable of solubility regulation is used as one means for improving the resolution of an isolated pattern. However, the resolution of an isolated pattern has not reached a satisfactory level.
Moreover, the microfabrication using a resist composition is not only directly used in the manufacturing of integrated circuits but also, in recent years, finds application in the production of so-called imprint mold structures, etc. (see, for example, patent reference 9 and non-patent reference 1). Therefore, it is an important task to simultaneously satisfy high sensitivity, high resolution (for example, high resolving power, excellent pattern shape and minute line edge roughness (LER)) and favorable dry etching resistance, and it is now needed to achieve this task.